Choosing a television
The world of televisions has changed dramatically in the past few years, with slim flat panel TVs replacing bulky old-style models, and digital signals increasingly taking over from analogue. Alongside some exciting improvements in viewing experience has come a proliferation of technical terms. Shoppers who are looking for a new TV now have to work out whether they want a plasma or an LCD screen, whether they want high definition pictures (HD), whether their screen resolution should be 786p or 1080i, and whether to plump for HD ready or Full HD.
These terms can be helpful, but are more likely to be confusing unless you know what they mean. In this guide we aim to help you cut a path through this jungle of terms to help you find the TV that is right for you.
5 Tips for buying a new TV
Digital vs analogue TV
Whitehaven in Cumbria made the news recently for being the first region to go completely digital. Between now and 2012 the whole country will be switching from an analogue to a digital signal.
There are a number of immediate advantages to going digital, as well as future-proofing yourself for when your region switches off the analogue signal. Digital signals don’t suffer from interference so you should have a clearer picture. Also, many programmes are broadcast in true widescreen, which is great for watching films (because the image doesn’t have to be ‘squashed’ to fit on the screen).
So what do you need to do in order to receive the new digital signal? There are three ways that you can do this:
1) Buy and connect a digital tuner (also known as a Freeview Box) to your existing television.
2) Get a television with a built-in digital tuner – these are called integrated digital televisions (IDTVs).
3) Cable and satellite providers offer free-to-view and subscription channels. You may need additional equipment for this, usually available directly from the supplier for a one-off payment.
The other big advantage is that you get many more channels, typically around 40.
The flatscreen technologies: Plasma and LCD
If you’re confused about the differences between LCD and plasma screens, we’ve got a simple rule: don’t be. At most screen sizes LCDs are all that is on offer. Its only at large screen sizes (above 37”) that plasma and LCD screens are still battling it out. Currently around 80% of TVs on the market are LCD screens.
If you are looking for a screen that costs below £500 or is smaller than 37”, then LCD is the way to go.
If you are looking for a larger or more expensive set than that, perhaps as the centrepiece of a home cinema set-up, you do need to decide which is right for you. Here is a summary of the differences between the two technologies.
LCD or liquid crystal displays are probably what you are using to read this page.
The advantages of LCDs are that they are generally cheaper at most sizes than equivalent plasma screens, are longer lasting and easier to look after, and use less energy.
LCD screens started out life as small computer displays, gradually increasing in size to the point where they have become able to compete with plasma screens in the above 37” market. LCD screens are made up of a grid of pixels, or points. They work by emitting light at each pixel, which acts like a mosaic to build up the overall image. If you want to display black pixels, you have to cover up the pixel, like covering up a lamp. It is this use of lots of individual pixels that allows LCD screens to function at very small sizes – each pixel basically works by itself to emit the colours required. The first disadvantage of this is that covering and uncovering each pixel each time you want to display black takes time, like the shutter speed on a camera, and limits what’s called the ‘response time’ – the amount of time it takes to change the pixel’s output. The upshot of all this is that when watching sports and other content with lots of fast-moving images, some LCD screens will have blurring.
The second inherent disadvantage of LCDs is that covering the pixel is not always complete, meaning that some light can seep out from the pixel. This means that blacks on LCD screens are often not as dark or rich as those on plasmas. Look out for the contrast ratio to get an idea of this.
Plasma screens create images in different way to LCD screens, giving them a different set of advantages and disadvantages. In a plasma screen an electric current causes light to be emitted from gas trapped between two layers of glass. For the screen to be energy efficient it has to be fairly large, meaning that plasma screens are currently only competitive above 37”.
To create black pixels, plasmas simply turn of the power supply to the appropriate pixels so they stop emitting any light. One advantage of this technology is that switching pixels on or off is as quick as switching an electric current on or off – much quicker than covering up a lamp, as in LCD TVs. So response times for plasma screens are generally better than for LCDs.
It also means that blacks are darker than in LCDs, since the pixels are not emitting any light at all. So look for better contrast ratios in plasma screens.
The main disadvantages of plasmas are that they are heavier and more expensive. Until recently they also suffered from a problem called ‘screen burn-in’. When left displaying a static image (like a logo on a 24 hour news channel) for a few hours, the pixels would continue to display that image after the channel had been changed. Newer plasmas claim to have solved or at least reduced this issue, but it is well worth checking if the reviews of any plasma you are interested in mention this issue.
Despite their differences, most of the technical terms used to talk about the picture quality and other features of the television are the same between plasma and LCD screens. Here’s our glossary of the key phrases:
Glossary
Contrast ratio: This figure is designed to tell you how much difference there is between dark and light colours on the TV. It is quoted as a ratio, between the brightest white and the darkest black. 500:1 means the brightest white is 500 times more bright than the darkest black. Plasma screens have historically boasted better contrast ratios than LCD screens.
Frequency is how often your TV refreshes the image, units of Hertz (Hz), which simply means number of refreshes per second. A TV with a 50 Hz refresh rate therefore refreshes the screen 50 times per second.
HDMI Interface: Like a scart interface but capable of carrying HD signals from or to other devices. You’ll need these to link your Playstation 3 or your HD DVD player to your HD-ready TV.
HD TV stands for high definition television and claims to offer better picture quality than standard definition (SD) TV.
HD ready is a standard used in Europe to make HD technology less confusing. The minimum requirements for a TV to wear an HD ready badge are:
• Minimum vertical resolution of 750 pixels (in widescreen format)
• Ability to display 720p and 1080i formats
• An HDMI or Digital Video Interface (DVI interface)
• It must be compatible with analogue HD sources (like camcorders)
HD 1080p (or Full HD) is a more advanced HD standard, which claims to show HD sources (which are usually in 1080 resolution) to their full potential. TVs bearing this mark must have:
• Minimum 1920×1080 resolution
• Ability to display 1080p format without distortion
Before getting too worked up about the differences between normal HD and 1080p HD, it’s worth noting that on a 32” or smaller screen the differences between 1080 and 768 are usually impossible to detect, although this depends on how good your eyesight is and how close to the TV you are sitting!
Reflection angle is simply a techy term for viewing angle. It’s designed to express how picture quality performs when it is looked at from an angle. This effect is only an issue for LCD TVs.
Response time is a similar measure to refresh rate. It specifies the time it takes for a pixel to change from being fully black to fully white to fully black again, in milliseconds (ms). A higher response time means a slower performing TV, which means fast moving images are more likely to become blurred.
Screen size in inches: the size of the TV’s screen measured diagonally from corner to corner.
Scart interfaces: Scart sockets are places where you can connect other devices to your TV. If you already have a DVD player, a VCR and a Playstation you might want to make sure your new TV has enough Scart interfaces so you don’t have to keep crawling round the back of the TV.
Screen format means the shape of the screen, which is expressed as a ratio between the width and the height of the screen. For example standard format screens (4:3) have the same shape as a 4×3 grid. These are increasingly being replaced by widescreen formats, which have a ratio between the width and the height of the screen of 16:9.
Vertical resolution in pixels: The number of pixels in your TV determines the maximum amount of detail it can display. Because most TVs have hundreds of thousands of pixels, it’s easier to quote the number of pixels across the vertical and horizontal edges. And because most TVs have the same screen shape, it’s simpler still to just quote one of these edges, by convention the vertical one.
By far the most common screen resolution is 768. This means the screen is 768 pixels high x 1395 pixels wide, for a total of just over one million pixels. An increasingly popular resolution is 1080, which offers a total resolution of over two million pixels.
Prepared November 2007